The coastal zones protect us by acting as an effective barrier against storm-surges, tsunamis, strong winds and other unannounced adverse weather patterns. They are threatened by various anthropogenic and natural factors which cause destabilization of the sand dunes, threats to wildlife amongst others. Erosion is one of the key factors responsible for the destabilization of the coastal zone.
The Ministry helps to protect those natural barriers of the coastline by promoting awareness and the implementation of effective storm water management, flood control, and coastal zone management practices. It enforces legislations, engage stakeholders and undertake specific actions through projects to ensure that vulnerable coastlines and beach fronts are managed and used in a sustainable manner. The Department uses different coastal protection methods (soft and =/or hard engineering) to protect the coastline.
1. Soft Engineering approaches
Soft engineering options are often less expensive than hard engineering options. They are usually more long-term with less impact on the environment.
1.1 Timber Piling
This method provides a physical barrier protecting unprotected dune-land from the direct hit of surging waves. Geo-textile fabrics are placed behind and across the length of the wooden structures to complement the wooden pilings to trap sand that is washed up with the onshore transport of sediments by wave action. Backfilling with coral fill and sand is implemented to allow the dune-land to recover more quickly than it would to further stabilize dune-land restoration and stabilize timber piling. This method has been used on Mahé, Praslin & La Digue.
1.2 Beach Nourishment
Beach replenishment or nourishment is a technique used in coastal defense management schemes. It involves importing sand off the beach and piling it on top of the existing sand. The imported sand, however, must be of a similar quality to the existing beach material so that it can integrate with the natural processes occurring there without causing any adverse effects.
1.3 Sand Dune Management
Sand dune stabilization or sand dune management is used to prevent the loss of sediment on the beach. This method can be further strengthened by coastal re-vegetation whereby selected coastal plants are planted to protect the dune-land vegetation and stability On Mahe, the introduction of public amenities such as car parks, footpaths, bollards and boardwalks, has helped to stop the removal of sediments by humans.
2. Hard Engineering approaches
Hard engineering options tend to be expensive, short-term options. They may also have a high impact on the landscape or environment and be unsustainable. Different engineering techniques are also used to protect the coastline from erosion, and these are sometimes used together with soft engineering techniques to provide ‘double protection’ to the coastline.
2.1 Rock Armoring
Rock armoring involves the placement of large rocks piled or placed at the foot of dunes in areas prone to erosion or in areas that have been severely eroded. Geo-textile fabric is usually placed behind and across the rock placements. The rocks absorb the wave energy and hold beach material. With time, the accretion of sand could result in the formation of new beaches.
Outcomes
The various projects undertaken by the Ministry has yielded positive effects. A summary of the positive benefits at the various project sites are summarised below:
Anse La Mouche Beach Front Project
Anse A La Mouche- Beach front is now protected from further erosion. The accretion of the sand has hep to rebuilt beach. Rehabilitation works has increased the aesthetic value of the area for both locals and tourists. As a result, the dune-land now provides a playground atmosphere where visitors can relax under the Takamaka trees, which are also stabilizing the dune-land. It is good to note that the re-vegetation of the dune-land critical in restoring buffer zone to protect inland plants from salt spray as well as protect establishments. The accretion of sand helping to rebuild the beach and protects the road from adverse effects of surging waves and from further erosion and scouring.
Anse Royale Project
The Anse Royale – Beach front protected from further erosion by installed rock armoring network. Accretion of sand helping to rebuild beach. Timber pilings stabilizing the dune-land and helping the beach to have a stable profile.
Cote D’Or Praslin
Timber pilings and backfilling is protecting the remaining dune land from further erosion and has also increased accretion in the area. This beach now has a stable profile and the infrastructures behind are well protected from surging waves.
North-East Point
The 360-metre of beach protected from coastal erosion caused by waves and heavy storms around this stretch of road. Measure has also protected damage to the road caused by erosion and helping to protect both traffic and pedestrians. It has also created a better and wider shoreline and gives the road a better gradient.
Grand Anse Boardwalk
The structure has allowed beach users to access the main beach by these designated ways, which in turn have allowed the dense coastal buffer vegetation to remain intact and free of trampling by foot access.
The Future
Ongoing monitoring of restored sites to assess efficiency of coastal protection works. Maintenance work planned where sites are being affected by adverse weather events. Ongoing sensitization programs to the general public on the importance of protecting coastlines not only for recreational purposes, but also regarding coastlines as providing essential environmental and anthropogenic services that provide benefits not only to us humans, but to the surrounding natural environment.